Problem: If $a + b + c = -6$ and $x + y + z = 3$, what is $-5z - 5y - 7b - 5x - 7a - 7c$ ?
Answer: $= -7a - 7b - 7c - 5x - 5y - 5z$ $= (-7) \cdot (a + b + c) + (-5) \cdot (x + y + z)$ $= (-7) \cdot (-6) + (-5) \cdot (3)$ $= 42 - 15$ $= 27$